There is a worldwide unmet need for technologies that simultaneously protect against human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs). Microbicides that concurrently protect against HIV and other STIs would address these health risks in an acceptable and affordable manner, and make a major contribution to public health globally. Also, a microbicide that has indications against STIs other than HIV may make use of such microbicide more acceptable to those not as concerned about HIV and thereby increase acceptability and adherence.
Unfortunately, previous studies with single active pharmaceutical ingredients (APIs) with broad anti-viral activity and ability to block different STIs in vitro or in vivo have not shown efficacy in clinical trials. The reasons for such lack of efficacy in clinical trials are unknown, but may be due to a variety of reasons, including e.g., low potency, short window of protection, reduction of activity in the presence of biological fluids, or induction of mucosal and microflora changes. Romano, J. W., et al., Non-specific microbicide product development: then and now. Current HIV research, 2012. 10(1): p. 9-18. Thus, there is a continuing need to identify more potent and safe APIs which may be used alone or in combination for microbicidal use.
Compounds with known in vivo microbicidal activity include the carrageenans. Carrageenans are polysaccharides which may be obtained from the red algae commonly known as seaweed. They are a structural component of seaweed and are extracted as three main types, namely iota, kappa and lambda, although there are other types as well, including kappa-II, mu and nu carrageenans. Carrageenans have been used extensively in the food, pharmaceutical, and cosmetics industries as thickeners, gelling agents, and stabilizing and dispersing agents. Extensive pharmacological and toxicological studies have been conducted. Carrageenan has been found to be non-toxic by oral, dermal, and inhalation routes of administrations even at extremely high doses. The carrageenans were therefore classified as “generally recognized as safe” (GRAS) by the FDA in 1972. Food and Drug Administration. GRAS (Generally recognized as safe) food ingredients: Carrageenan. FDA Publications PB-221 206, (1972).
Further extensive oral pharmacokinetic studies conducted in pigs, rats, mice, gerbils, guinea pigs, ferrets, hamsters, dogs, and monkeys showed that the breakdown of the carrageenans in the gastrointestinal tract was minimal at best and that absorption was virtually non-existent. Benitz, K. F., et al., Toxicol. Appi. Pharmacol. 22, 282 (1972); Fox, M. R. S. & Jacobs, R. M. Metal Ions in Biological Systems, pp. 214-248 (Marcel Decker, Inc., 1986); Luscombe, D. K. & Nicholls, P. J. Fd. Cosmet. Toxicol. 11, 229-237 (1973); Naess, B. Acta Vet. Scand. 12, 592-600. 1971; Samman, S. & Roberts, D. C. K., Med. J. Australia 146, 246-249 (1987); U.S.EPA. Health Effects Assessment of for Zinc (and Compounds). EPA/540-1-96-048. 1984. Washington, D.C., US Environmental Protection Agency, Office of Research and Development; Walden, J. T. & Derreth, D. FDA New Release 72/55. FDA Publications 72/55, (1972); Walker, A. P. et al. Fd. Chem. Toxic. 35, 1099-1106 (1997); Weiner, M. L. Intestinal transport of some macromolecules in food. Fd. Chem. Toxic. 26, 10, 867-880 (1988).
International Patent Publication WO 94/15624 teaches use of sulfated polysaccharides such as iota carrageenan, dextran sulfate, kappa carrageenan, lambda carrageenan, heparin mimetics, heparin sulfate, pentosan polysulfate, chondrotin sulfate, lentinan sulfate, curdlan sulfate, de-N-sulfated heparin and fucoidan, to inhibit cell-to-cell transmission of HIV and thus the sexual transmission of Acquired Immune Deficiency Syndrome (AIDS), as well as Chlamydia organism. This publication teaches that iota carrageenan is the most efficacious of the commercially available sulfated carrageenans in preventing HIV infection and in blocking Chlamydia infection in vitro and in vivo.
Zinc is another known inhibitor of such sexually transmitted pathogens as HIV and Herpes simplex virus 2 (HSV-2). Zinc acetate (ZA) and zinc sulfate have been shown to inhibit HIV infection in cell culture, and HSV-2 in both cell culture and laboratory animals. Zinc salts have been shown to be effective in blocking infection by HIV in vitro (Haraguchi, Y., et al. Antiviral Res 43, 123-133 (1999)) and also blocking infection by foot-and-mouth virus, human rhinovirus, influenza A and B, semliki forest virus and sindbis virus. Sergio, W. Medical Hypotheses 26, 253 (1988). Haraguchi, et al. found that zinc chloride, cadmium acetate and mercury chloride inhibited HIV-1 production as assayed by p24 ELISA and RT. Zinc chloride did not exhibit significant cytotoxicity when present in concentrations of up to 550 μg/mL.
Lectins are carbohydrate binding proteins which may have roles in the immune system by binding to carbohydrates present on invading pathogens. The lectin known as Griffithsin (GFRT or G) has been reported to have potent anti-HIV activity, and can block HIV replication in vitro at subnanomolar concentrations (IC50 values 0.02 to 0.8 nM). See Alexandre, K. B., et al., Virology, 2012. 423(2): p. 175-86; Huskens, D. and D. Schols, Marine Drugs, 2012, 10(7): p. 1476-97; Mori, T., et al., The Journal of biological chemistry, 2005. 280(10): p. 9345-53; and also U.S. Pat. No. 8,088,729, the contents of all of which are incorporated by reference herein in their entirety.
Griffithsin can be produced in multigram quantities in tobacco plants. O'Keefe, B. R., et al., Proceedings of the National Academy of Sciences of the United States of America, 2009. 106(15): p. 6099-104. Notably, GRFT resists degradation by several proteases, is highly stable even at high temperatures, is non-irritating, does not induce cellular activation, and induces only minimal changes in secretion of inflammatory cytokines and chemokines by blood or epithelial cells. O'Keefe, B. R., et al., Proceedings of the National Academy of Sciences of the United States of America, 2009. 106(15): p. 6099-104; Kouokam, J. C., et al., PloS one, 2011. 6(8): p. e22635; Moncla, B. J., et al., Advances in bioscience and biotechnology, 2011. 2(6): p. 404-408.
Griffithsin has shown excellent safety and efficacy against HIV in explant models, and modified forms of GRFT have been reported as having improved potency, stability, and solubility. O'Keefe, B. R., et al., Proceedings of the National Academy of Sciences of the United States of America, 2009. 106(15): p. 6099-104. GRFT also has been shown to have in vivo activity against HSV-2. Nixon, B., et al., Journal of virology, 2013. 87(11): p. 6257-69.
Applicants have previously reported that a complex between a water-soluble metal salt and carrageenans can provide anti-microbial effects. The water-soluble metal salt can be a zinc metal, and in a particular embodiment, a combination of zinc acetate (ZA) formulated in a carrageenan gel has been shown to be active against HIV, HSV-2, human papillomavirus (HPV), and T. vaginalis. Fernandez-Romero, J. A., et al., Antimicrobial agents and chemotherapy, 2012. 56(1): p. 358-68; Kenney, J., et al., Antimicrobial Agents and Chemotherapy, 2013. 57(8): p. 4001-9. See also, U.S. Pat. No. 8,567,098 the entire contents of which are incorporated by reference herein. Notwithstanding, the need for additional broad spectrum, more potent microbicides which can protect against HIV and/or other STIs still exists.